"Communication is What the Listener Does"

The guys at Manager Tools have a saying: "Communication is what the listener does." 

Sidebar: if you're in business, or manage people, you need to listen to Manager Tools -- free podcasts, outstanding content! 

There's truth here for Bible teachers.  You may think all the communication rests on you, but the key part rests with the people you are teaching.  No learning happens without their engagement.  Let me say that again, clearly: No learning happens without their engagement.

Therefore you want to make it easy for them to learn from you, by keeping them engaged.  Make it easy and enjoyable for them to listen (even if the message is sometimes hard).  Don't overload them, or it will all drain out the ears without getting in any deeper.